The Unit on Molecular Physiology has extended its RT-PCR work on large- scale temporal gene expression to hippocampus (70 genes, 9 developmental time points, and perturbation by seizure). A manuscript is in preparation. This project has provided insights into the nature of the genetic network governing neural development, including apparent quasi- independent sub-networks of interacting genes within the larger genetic network. Equally important, these data have been compared with those obtained from spinal cord (112 genes, 9 developmental time points, obtained during FY96), and indicate which genes distinguish spinal from hippocampal development. Furthermore, there is an indication of a recapitulation of developmental programs in response to seizure. Progress has been made extending this work from tissue homogenate to the level of cell type by assaying gene expression in FACS-sorted cells from cerebral cortex. Computational work in this Unit during FY97 included a study of the distribution of information across "genes" which act combinatorially (manuscript in press), and collaborations on computational methods for analysis of actual large-scale temporal gene expression data (manuscripts accepted). A manuscript discussing the major theoretical issues regarding the functional genome, including infor mation transmission from genome to phenotype, has been nearly completed.